Temperature sensors are commonly used in several locations in a vehicle, in order to improve the operation of the vehicle. They may be located, for example, in an intake air stream, or in a coolant stream when contained in a brass bulb. These sensors need to be accurate and reliable while operating in the harsh vehicle environment over a long period of time. Further, since there may be several sensor assemblies per vehicle, the cost of the sensors must be minimized.
A temperature sensor used on a vehicle may, for example, include a pair of terminals, connected to a wiring harness, and also welded to a pair of wires. The wires are, in turn, soldered to a disc shaped thermistor. But this includes several electrical connections and is difficult to work with during assembly because of the wires, thus not lend itself well to automated assembly techniques. This, then, makes accurate location of the temperature sensor more difficult. To avoid the concerns created by the wires, one might employ a temperature sensor mounted on a substrate, which is then mounted to terminals. However, this would limit the temperature at which the assembly could operate because of the thermal expansion differences between the sensor element and the substrate material. In addition, concerns with defects in the substrate arise.
A desire exists, then, to maintain high reliability and accuracy over a wide temperature range in a harsh vehicle environment, while minimizing the cost of the sensor assembly. Further, it is desirable to have a sensor assembly arrangement that lends itself to automated assembly, to further minimize the cost.